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We report on over 13 years of optical and near-ultraviolet spectropolarimetric observations of the famous Luminous Blue Variable (LBV), P Cygni. LBVs are a critical transitional phase in the lives of the most massive stars, and achieve the largest mass-loss rates of any group of stars. Using spectropolarimetry, we are able to learn about the geometry of the near circumstellar environment surrounding P Cygni and gain insights into LBV mass-loss. Using data from the HPOL and WUPPE spectropolarimeters, we estimate the interstellar polarization contribution to P Cygni's spectropolarimetric signal, analyze the variability of the polarization across the H$\alpha$ emission line, search for periodic signals in the data, and introduce a statistical method to search for preferred position angles in deviations from spherical symmetry which is novel to astronomy. Our data are consistent with previous findings, showing free-electron scattering off of clumps uniformly distributed around the star. This is complicated, however, by structure in the percent-polarization of the H$\alpha$ line and a series of previously undetected periodicities.

We present new spectropolarimetric data for WR 42 collected over 6 months at the 11-m Southern African Large Telescope (SALT) using the Robert Stobie Spectrograph., 2 pages, 1 figure, accepted for publication in RNAAS

Liquid lens coupling provides excellent transmission efficiency when compared to multilayer coatings especially for applications where broadband transmission is required. However, long term reliability of liquid coupling is difficult to achieve. This is typically due to chemical compatibility issues affecting both the optical transmission and the integrity of the opto-mechanical support. As part of a recent service of the Robert Stobie Spectrograph on SALT we had the opportunity to study these problems further and in this paper we provide analysis of problems identified and some solutions to prevent them. We also present general guidelines which could aid future opto-mechanical designs for liquid coupling of lenses.

We report the discovery of two new Galactic candidate luminous blue variable (LBV) stars via detection of circular shells (typical of confirmed and candidate LBVs) and follow-up spectroscopy of their central stars. The shells were detected at 22 µm in the archival data of the Mid-Infrared All Sky Survey carried out with the Wide-field Infrared Survey Explorer (WISE). Follow-up optical spectroscopy of the central stars of the shells conducted with the renewed Southern African Large Telescope (SALT) showed that their spectra are very similar to those of the well-known LBVs P Cygni and AG Car, and the recently discovered candidate LBV MN112, which implies the LBV classification for these stars as well. The LBV classification of both stars is supported by detection of their significant photometric variability: one of them brightened in the R and I bands by 0.68 ± 0.10 and 0.61 ± 0.04 mag, respectively, during the last 13–18 years, while the second one (known as Hen 3-1383) varies its B, V, R, I and Ks brightnesses by ˜0.5–0.9 mag on time-scales from 10 d to decades. We also found significant changes in the spectrum of Hen 3-1383 on a time-scale of ˜3 months, which provides additional support for the LBV classification of this star. Further spectrophotometric monitoring of both stars is required to firmly prove their LBV status. We discuss a connection between the location of massive stars in the field and their fast rotation, and suggest that the LBV activity of the newly discovered candidate LBVs might be directly related to their possible runaway status.

Polarization has been detected at early times for all types of supernova, indicating that such systems result from or quickly develop some form of asymmetry. In addition, the detection of strong line polarization in supernovae is suggestive of chemical inhomogeneities ("clumps") in the layers above the photosphere, which may reflect hydrodynamical instabilities during the explosion. We have developed a fast, flexible, approximate semi-analytic code for modeling polarized line radiative transfer within 3-D inhomogeneous rapidly-expanding atmospheres. Given a range of model parameters, the code generates random sets of clumps in the expanding ejecta and calculates the emergent line profile and Stokes parameters for each configuration. The ensemble of these configurations represents both the effects of various host geometries and of different viewing angles. We present results for the first part of our survey of model geometries, specifically the effects of the number and size of clumps (and the related effect of filling factor) on the emergent spectrum and Stokes parameters. Our simulations show that random clumpiness can produce line polarization in the range observed in SNe Ia (~1-2%), as well as the Q-U loops that are frequently seen in all SNe. We have also developed a method to connect the results of our simulations to robust observational parameters such as maximum polarization and polarized equivalent width in the line. Our models, in connection with spectropolarimetric observations, can constrain the 3-D structure of supernova ejecta and offer important insight into the SN explosion physics and the nature of their progenitor systems., Accepted to ApJ; 19 pages, 15 figures

We report the discovery of the first symbiotic star (V=21.6, K_S=15.8 mag) in the Local Group dwarf irregular galaxy NGC6822. This star was identified during a spectral survey of Ha emission-line objects using the Southern African Large Telescope (SALT) during its performance-verification phase. The observed strong emission lines of HI and HeII suggest a high electron density and T* < 130 000 K for the hot companion. The infrared colours allow us to classify this object as an S-type symbiotic star, comprising a red giant losing mass to a compact companion. The red giant is an AGB carbon star, and a semi-regular variable, pulsating in the first overtone with a period of 142 days. Its bolometric magnitude is M_bol=-4.4 mag. We review what is known about the luminosities of extragalactic symbiotic stars, showing that most, possibly all, contain AGB stars. We suggest that a much larger fraction of Galactic symbiotic stars may contain AGB stars than was previously realised., 6 pages, 4 figures, accepted to MNRAS

In this work we present the first spectroscopic results obtained with the Southern African Large Telescope (SALT) telescope during its perfomance-verification phase. We find that the Sagittarius dwarf spheroidal galaxy (Sgr) Sgr contains a youngest stellar population with [O/H] -0.2 and age t>1 Gyr, and an oldest population with [O/H]=-2.0. The values are based on spectra of two planetary nebulae (PNe), using empirical abundance determinations. We calculated abundances for O, N, Ne, Ar, S, Cl, Fe, C and He. We confirm the high abundances of PN StWr2-21 with 12+log(O/H) = 8.57+/-0.02 dex. The other PN studied, BoBn1, is an extraordinary object in that the neon abundance exceeds that of oxygen. The abundances of S, Ar and Cl in BoBn1 yield the original stellar metallicity, corresponding to 12+log(O/H) = 6.72+/-0.16 dex which is 1/110 of the solar value. The actual [O/H] is much higher: third dredge-up enriched the material by a factor of ~12 in oxygen, ~240 in nitrogen and ~70 in neon. Neon as well as nitrogen and oxygen content may have been produced in the intershell of low-mass AGB stars. Well defined broad WR lines are present in the spectrum of StWr2-21 and absent in the spectrum of BoBn1. This puts the fraction of [WR]-type central PNe stars to 67% for dSph galaxies., 14 pages, 4 figures, accepted to MNRAS

We report the discovery of optical ghosts generated when using Volume Phase Holographic (VPH) gratings in spectrographs employing the Littrow configuration. The ghost is caused by light reflected off the detector surface, recollimated by the camera, recombined by, and reflected from, the grating and reimaged by the camera onto the detector. This recombination can occur in two different ways. We observe this ghost in two spectrographs being developed by the University of Wisconsin - Madison: the Robert Stobie Spectrograph for the Southern African Large Telescope and the Bench Spectrograph for the WIYN 3.5m telescope. The typical ratio of the brightness of the ghost relative to the integrated flux of the spectrum is of order 10^-4, implying a recombination efficiency of the VPH gratings of order 10^-3 or higher, consistent with the output of rigorous coupled wave analysis. Any spectrograph employing VPH gratings, including grisms, in Littrow configuration will suffer from this ghost, though the general effect is not intrinsic to VPH gratings themselves and has been observed in systems with conventional gratings in non-Littrow configurations. We explain the geometric configurations that can result in the ghost as well as a more general prescription for predicting its position and brightness on the detector. We make recommendations for mitigating the ghost effects for spectrographs and gratings currently built. We further suggest design modifications for future VPH gratings to eliminate the problem entirely, including tilted fringes and/or prismatic substrates. We discuss the resultant implications on the spectrograph performance metrics., Comment: 13 pages, 8 figures, emulateapj style, accepted for publication in PASP

We report the serendipitous discovery of the Sloan Digital Sky Survey star, SDSS J160043.6+074802.9 to be a very rapid pulsator. The variation is dominated by a frequency near 8380 microHz (period = 119.33 s) with a large amplitude (0.04 mag) and its first harmonic at 16760 microHz (59.66 s; 0.005 mag). In between these frequencies, we find at least another 8 variations with periods between 62 and 118 seconds and amplitudes between about 0.007 and 0.003 mag; weaker oscillations might also be present. Preliminary spectrograms from the performance verification phase of the Southern African Large Telescope indicate that SDSS J160043.6+074802.9 is a spectroscopic binary consisting of an sdO star and a late-type main-sequence companion. This makes it the first unambiguous detection of such an sdO star to pulsate, and certainly the first found to exhibit multi-frequency variations., 7 pages, 6 figures (figure 4 at reduced resolution, original available on request). Accepted for publication in MNRAS

The recently completed Southern African Large Telescope (SALT) is a low cost, innovative, 10 m class optical telescope, which began limited scientific operations in August 2005, just 5 years after ground-breaking. This paper describes the design and construction of SALT, including the first-light instruments, SALTICAM and the Robert Stobie Spectrograph (RSS). A rigorous systems engineering approach has ensured that SALT was built to specification, on budget, close to the original schedule and using a relatively small project team. The design trade-offs, which include an active spherical primary mirror array and a fixed altitude telescope with a prime focus tracker, although restrictive in comparison to conventional telescopes, have resulted in an affordable 10 m class telescope for South Africa and its ten partners. Coupled with an initial set of two seeing-limited instruments that concentrate on the UV-visible region (320 – 900 nm) and featuring some niche observational capabilities, SALT will have an ability to conduct some unique science. This includes high time resolution studies, for which some initial results have already been obtained. Many of the versatile modes available with the RSS - which is currently being commissioned - are unique and provide unparallelled opportunities for imaging polarimetry and spectropolarimetry. Likewise, Multi-Object Spectroscopy (with slit masks) and imaging spectroscopy with the RSS, the latter using Fabry-Perot etalons and interference filters, will extend the multiplex advantage over resolutions from 300 to 9000 and fields of view of 2 to 8 arcminutes. Future instrumentation plans include an extremely stable, fibre-fed, high resolution echelle spectrograph and a near-IR (to between 1.5 to 1.7 m) extension to the RSS. Future development possibilities include phasing the primary mirror and AO. Finally, extrapolations of the SALT/HET designs to ELT proportions remain viable and are surely more affordable than conventional, fully steerable, designs.

The wavelength dependence of interstellar polarization due to dust in M31 has been observed along four sightlines. Only one sightline had been measured previously.The globular clusters, S78, S150, S233 and Baade 327 were used as point sources to probe the interstellar dust in M31. The Serkowski law produces good fits for all the sightlines although the relationship between K and lambda(max) may be different from that found in the Galaxy. The results of this study imply that the slope K/lambda(max) may be significantly larger in M31. The Serkowski curves are significantly narrower than those of the same lambda(max) in the Galaxy and may require extreme modifications to the size distributions of silicate particles. The fits for the four sightlines reveal values of lambda(max) ranging from 4800 to 5500 A. These are consistent with average values of lambda(max) measured in the Galaxy and the Magellanic Clouds. The range measured for M31 corresponds to R(V) values of 2.7 to 3.1. The range in R(V) seen in the Galaxy is 2.5 to 5.5 implying, for this small sample, that the average size ofinterstellar grains in M31 is typically smaller than that seen for Galactic grains if the nature of the grains is the same. Also, the polarization efficiency for these sightlines is large although some bias is expected since sightlines known to have significant interstellar polarization were selected for the sample., Comment: 13 pages, 2 figures, AJ in press (June)

We have used wide-field ultraviolet, optical, and far-infrared photometric images of Pleiades reflection nebulosity to analyze dust properties and the three-dimensional nebular geometry. Scattered light data were taken from 1650 and 2200 A Wide-Field Imaging Survey Polarimeter images and a large 4400 A mosaic of Burrell Schmidt CCD frames. Dust thermal emission maps were extracted from IRAS data. The scattering geometry analysis is complicated by the blending of light from many stars and the likely presence of more than one scattering layer. Despite these complications, we conclude that most of the scattered light comes from dust in front of the stars in at least two scattering layers, one far in front and extensive, the other nearer the stars and confined to areas of heavy nebulosity. The first layer can be approximated as an optically thin, foreground slab whose line-of-sight separation from the stars averages ~0.7 pc. The second layer is also optically thin in most locations and may lie at less than half the separation of the first layer, perhaps with some material among or behind the stars. The association of nebulosities peripheral to the main condensation around the brightest stars is not clear. Models with standard grain properties cannot account for the faintness of the scattered UV light relative to the optical. Some combination of significant changes in grain model albedo and phase function asymmetry values is required. Our best-performing model has a UV albedo of 0.22 ± 0.07 and a scattering asymmetry of 0.74 ± 0.06. Hypothetical optically thick dust clumps missed by interstellar sight line measurements have little effect on the nebular colors but might shift the interpretation of our derived scattering properties from individual grains to the bulk medium.

We present new wide-field optical and ultraviolet images of the Pleiades reflection nebula that allow a more thorough evaluation of the dust scattering than any prior data set. Vacuum-UV images were taken at 1650 and 2200 A during the first flight of the Wide-Field Imaging Survey Polarimeter (WISP), a sounding rocket-borne telescope. WISP captured the brighter parts of the nebula at both wavelengths, with 3 σ sensitivities of 22.5 and 23.4 UV mag arcsec-2, respectively. The 50 × 17 WISP field was also mapped at 4400 A with a mosaic of 40 Burrell Schmidt CCD frames using a broadband BJ filter. The Schmidt mosaic shows extensive and intricate nebulosity down to a 5 σ sensitivity limit of 27.6 B mag arcsec-2, including features undetected by photographic surveys. We explore the intensity and color behavior of the nebula in our UV and optical images and far-infrared IRAS data. We find that the photometric structure near bright stars is more complex than previous studies have implied, but general trends are still apparent. The color gradients around the stars are caused by phase function effects rather than internal reddening. The greater concentration of scattered light versus thermal emission indicates that most of the observed scattering is from foreground dust. A somewhat greater concentration of UV versus optical light suggests grain scattering is more forward-directed at shorter wavelengths. The UV nebula is much fainter than expected from the stellar photometry and interstellar reddening. Explaining this UV faintness requires either more reddening than is measured or significant alterations to current dust property estimates.

The HPOL spectropolarimeter, previously operated by the University of Wisconsin at Pine Bluff Observatory (PBO), has been restored and relocated to the University of Toledo's Ritter Observatory. We achieved first light with HPOL at Ritter Observatory on 2012 March 11. We present a detailed instrument description of HPOL in its current configuration at Ritter Observatory, and a description of the standard observing procedure. We performed frequent observations of unpolarized standard stars to calibrate the instrumental polarization. We present polarimetric calibration results for observations spanning 2012 March 11 to 2013 May 2. Our calibration work shows that the systematic uncertainties of observations obtained with HPOL at Ritter Observatory are comparable to, and sometimes outperform, the systematic uncertainties obtained at PBO. We have successfully recommissioned the HPOL spectropolarimeter at Ritter Observatory, making it once again available for ongoing science observations.

The Southern African Large Telescope (SALT) currently has three instruments: the imaging SALTICAM, the new High Resolution Spectrograph (HRS) which is in the process of being commissioned and the Robert Stobie Spectrograph (RSS). RSS has multiple science modes, of which long slit spectroscopy was originally commissioned; We have commissioned two new science modes: Multi Object Spectroscopy (MOS) and Fabry-Perot (FP). Due to the short track times available on SALT it is vital that acquisition is as efficient as possible. This paper will discuss how we implemented these modes in software and some of the challenges we had to overcome. MOS requires a slit-mask to be aligned with a number of stars. This is done in two phases: in MOS calibration the positions of the slits are detected using a through-slit image and RA/DEC database information, and in MOS acquisition the detector sends commands to the telescope control system (TCS) in an iterative and interactive fashion for fine mask/detector alignment to get the desired targets on the slits. There were several challenges involved with this system, and the user interface evolved to make the process as efficient as possible. We also had to overcome problems with the manufacturing process of the slit-masks. FP requires the precise alignment each of the two etalons installed on RSS. The software makes use of calibration tables to get the etalons into roughly aligned starting positions. An exposure is then done using a calibration arc lamp, producing a ring pattern. Measurement of the rings allows the determination of the adjustments needed to properly align the etalons. The software has been developed to optimize this process, along with software tools that allow us to fine tune the calibration tables. The software architecture allows the complexity of automating the FP calibration and procedures to be easily managed.

The Robert Stobie Spectrograph Near Infrared Instrument (RSS-NIR), a prime focus facility instrument for the 11-meter Southern African Large Telescope (SALT), is well into its laboratory integration and testing phase. RSS-NIR will initially provide imaging and single or multi-object medium resolution spectroscopy in an 8 arcmin field of view at wavelengths of 0.9 - 1.7 μm. Future modes, including tunable Fabry-Perot spectral imaging and polarimetry, have been designed in and can be easily added later. RSS-NIR will mate to the existing visible wavelength RSS-VIS via a dichroic beamsplitter, allowing simultaneous operation of the two instruments in all modes. Multi-object spectroscopy covering a wavelength range of 0.32 - 1.7 μm on 10-meter class telescopes is a rare capability and once all the existing VIS modes are incorporated into the NIR, the combined RSS will provide observational modes that are completely unique. The VIS and NIR instruments share a common telescope focal plane, and slit mask for spectroscopic modes, and collimator optics that operate at ambient observatory temperature. Beyond the dichroic beamsplitter, RSS-NIR is enclosed in a pre-dewar box operating at -40 °C, and within that is a cryogenic dewar operating at 120 K housing the detector and final camera optics and filters. This semi-warm configuration with compartments at multiple operating temperatures poses a number of design and implementation challenges. In this paper we present overviews of the RSSNIR instrument design and solutions to design challenges, measured performance of optical components, detector system optimization results, and an update on the overall project status.

Departures from spherical symmetry are known to exist around Luminous Red Variables (LRVs). One of the earliest pieces of evidence came from the discovery that light from these objects is polarized. Additional evidence comes from other techniques and observations of related objects. This talk briefly reviews these data and focuses on the mechanisms that produce polarization in LRVs. Emphasis is given on recent spectropolarimetric monitoring data of selected key objects and what we have learned about the LRV environment from such data.

Polarimetry has proven to be a useful observational tool in the study of Be stars. In recent years, Monte Carlo radiative transfer methods have often been used in modeling polarimetric measurements, since they allow accurate predictions of flux and polarization via numerical simulation of the interaction of light with matter, even in systems with complex configurations. We have extended these two complementary techniques to the investigation of binary Be stars by developing a Monte Carlo code that models the flux and polarization phase curves of a binary-disk system. We here present the latest results matching geometrical model configurations with our own spectropolarimetric observations of the Algol binary β Lyrae.

Motivated by new sounding-rocket wide-field polarimetric images of the Large Magellanic Cloud, we have used a three-dimensional Monte Carlo radiation transfer code to investigate the escape of near-ultraviolet photons from young stellar associations embedded within a disk of dusty material (i.e. a galaxy). As photons propagate through the disk, they may be scattered or absorbed by dust. Scattered photons are polarized and tracked until they escape to be observed; absorbed photons heat the dust, which radiates isotropically in the far-infrared, where the galaxy is optically thin. The code produces four output images: near- UV and far-IR flux, and near-UV images in the linear Stokes parameters Q and U. From these images we construct simulated UV polarization maps of the LMC. We use these maps to place constraints on the star + dust geometry of the LMC and the optical properties of its dust grains. By tuning the model input parameters to produce maps that match the observed polarization maps, we derive information about the inclination of the LMC disk to the plane of the sky, and about the scattering phase function g. We compute a grid of models with i = 28 deg., 36 deg., and 45 deg., and g = 0.64, 0.70, 0.77, 0.83, and 0.90. The model which best reproduces the observed polarization maps has i = 36 +2/-5 degrees and g ~0.7. Because of the low signal-to-noise in the data, we cannot place firm constraints on the value of g. The highly inclined models do not match the observed centro-symmetric polarization patterns around bright OB associations, or the distribution of polarization values. Our models approximately reproduce the observed ultraviolet photopolarimetry of the western side of the LMC; however, the output images depend on many input parameters and are nonunique., Accepted to AJ. 20 pages, 7 figures

A magnetic —eld diagnostic of stellar winds that uses the Hanle eUect is discussed. This diagnostic pertains to the modi—cation of resonance-linescattering polarization in the presence of magnetic —elds. The case for resolved polarized pro—les of optically thin emission lines is considered, and some analytic results for an expanding equatorial disk are derived. Numerical results for a dipole magnetic —eld embedded in a spherical out—ow are also presented. Although the considerations are somewhat simpli- —ed, the primary conclusion is that the modi—cation or creation of line pro—le polarization by the Hanle eUect can be used to discriminate between diUerent magnetic —eld geometries and to estimate the mag- netic —eld strength in the region of line formation. Subject headings: line: formationpolarizationscatteringstars: atmospheres ¨ stars: magnetic —elds

Portions of the Moon were observed by the Wisconsin Ultraviolet Photopolarimeter Experiment (WUPPE) on 1995 March 12, 14 and 17, and represent the first ultraviolet (UV) spectropolarimetric observations of the Moon. The polarimetric observations confirm that a change in the dominant scattering process occurs in the UV, changing from volume scattering in the near-UV to surface scattering in the far-UV. The data are investigated empirically. It is found that Umov's relationship holds when the polarization is perpendicular to the scattering plane. It is also found that the degree of polarization can be modelled by a phase-angle-dependent polarization modified by a wavelength-dependent depolarization factor. The scattering function for each observation is determined.

We present ultraviolet and visual spectropolarimetry of the interacting binary star β Lyrae, obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment and the HPOL spectropolarimeter at Pine Bluff Observatory. Our observations span 3 years and cover the wavelength range from 1400 to 10500 A, with a resolution of 7.5–16 A. Detailed broad- and narrowband spectropolarimetric analysis allows us to begin to decompose the complex spectrum of β Lyr: by examining the polarization behavior of a line or continuum, we can determine which component scatters the light and, ultimately, from which component that light originates. After removing interstellar polarization from our data and rotating the results to the apparent intrinsic position angle of the system, we find that the polarization of the hydrogen Balmer and vacuum ultraviolet "UV bump" emission lines, as well as that of the near-UV continuum, remains mostly constant with phase and is oriented at 90° to the visible polarization, indicating that the scattering plane of the light in these three spectral components is perpendicular to the scattering plane of the visible light. We propose that the UV bump, Balmer emission, and near-UV continuum polarization is produced by electron scattering within a bipolar outflow in the β Lyr system. The intrinsic visible polarization of β Lyr shows eclipses that associate it with material near the accretion disk. We find conflicting evidence regarding both the origin of this visible light and the scattering surface that polarizes it: continuum evidence points toward the secondary object as the illuminator and the accretion disk edge as the scatterer, while line analysis suggests that light from the loser scatters off material between it and the disk. The presence of material away from the orbital plane may help resolve this contradiction.

The Hanle effect concerns the modification of polarized resonance-line scattering by magnetic fields; thus, it can be used as a diagnostic of stellar magnetic fields. The Hanle effect has been used to determine the field strength and distribution of magnetic structures present in prominences of the Sun. To investigate its potential use in stellar astronomy, the simplified case of an optically thin axisymmetric ring illuminated by a stellar point source is considered. The results are then used to derive the polarization from polar plumes, equatorial disks, and spherical shells. The integrated line polarization is calculated for axisymmetric rings with a variety of magnetic field orientations, and in every case the polarization is proportional to sin2 i (where i is the viewing inclination), just as in the zero field case. It is also found that the Hanle effect can significantly alter the integrated line polarization. In some cases the position angle of the polarization in the line can be rotated by 90° relative to the zero field case. We consider the Hanle effect as a possible diagnostic of magnetic fields in stellar winds with prominent ultraviolet and visible resonance lines. For these lines the diagnostic has sensitivity in the range of 1-1000 G. The Zeeman effect is not normally applicable for diagnosing magnetic fields in stellar winds in the subkilogauss range; thus, the Hanle effect should provide an especially useful new method of determining magnetic fields in stars other than the Sun. Possibilities for measuring the fields in early-type stars using ultraviolet observations is discussed.

The R Coronae Borealis (RCB) stars produce dust at irregular intervals, but the distribution of the circumstellar material is not known. We report spectropolarimetry of R Coronae Borealis (R CrB) itself, obtained in a deep decline with the Wisconsin-Indiana-Yale-NOAO telescope. The continuum is polarized ~1% in the red, rising to ~2% in the blue. There are significant polarization variations across the emission lines. The polarization of the Na I D lines indicates that light from the emission-line region is scattered but at a different angle from the stellar continuum. The position angle of the continuum polarization is almost constant from 1 μm to 7000 A but then changes rapidly, rotating by ~60° between 7000 and 4000 A. This behavior is strikingly similar to that produced in post-asymptotic giant branch (AGB) stars having an obscuring torus and bipolar dust lobes. These new data strengthen the earlier suggestion that there is a preferred direction to the dust ejections in R CrB. Dust ejections seem to occur predominantly along two roughly orthogonal directions consistent with a bipolar geometry. If confirmed, this finding will reinforce the relationship between the RCB stars and other post-AGB stars.

We report on the reduction and analysis of UVpolarimetric images of CI (λ1657 A) and dust continuum (2696 A emissions from C/1995 O1 (Hale-Bopp) taken using the Wide Field Imaging Survey Polarimeter (WISP) sounding rocket on 8 April, 1997. These observations represent the first imaging polarimetry of comets in the UV, and were performed in consort with ground based measurements of gas and dust polarization and distribution. The continuum results show 9% polarization across the image field with a polarization phase angle close to the 129° prediction. Comparison with ground based data implies minimal color dependence for Hale-Bopp in either the degree of polarization and in the position angle. The carbon polarimetry implies that most production occurs in the dense inner coma, and that it leaves that area in thermodynamic equilibrium. Its radial profile further constrains the carbon outflow speed to be sufficient to travel ≥5 × 106 km without photoionization.

A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent), and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition., Comment: 12 pages, 10 figures, accepted for publication in MNRAS

The Southern African Large Telescope (SALT) began its re-commissioning phase in April 2011 following the completion of remedial engineering work on the telescope and the major science instrument, the Robert Stobie Spectrograph (RSS). The engineering work required modifications to the spherical aberration corrector, in order to improve the telescope’s image quality, and RSS, to improve its throughput. Positive test results included delivery of sub-arcsecond images, essentially meeting the original telescope image quality specifications and exhibiting none of the previous field-dependent aberrations, while the RSS has shown greatly improved efficiency performance. SALT has since transitioned to science operations, as from 1 September 2011, following the first open call for charged science proposals from the SALT partners. This paper discusses the current performance of SALT and it First Generation instruments, some initial science results, the proposal process and the operational model for the telescope.

We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one of the least luminous SNe IIb or Ib observed to date. Our observations begin with a discovery within 1 day of explosion and span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly and are replaced by Type Ib-like He-rich features on the timescale of one week. High-cadence monitoring of this transition suggests that absorption attributable to a high velocity (> 12,000 km/s) H-rich shell is not rare in Type Ib events. Radio observations imply a shock velocity of v = 0.13c and a progenitor star mass-loss rate of 1.4 x 10^{-5} Msun yr^{-1} (assuming wind velocity v_w=10^3 km/s). This is consistent with independent constraints from deep X-ray observations with Swift-XRT and Chandra. Overall, the multi-wavelength properties of SN 2011ei are consistent with the explosion of a lower-mass (3-4 Msun), compact (R*, 20 pages, 19 figures, accepted for publication in the Astrophysical Journal

On the final day of the Stellar Polarimetry conference, participants split up into three "breakout sessions" to discuss the future of the field in the areas of instrumentation, upcoming opportunities, and community priorities. This contribution compiles the major recommendations arising from each breakout session. We hope that the polarimetric community will find these ideas useful as we consider how to maintain the vitality of polarimetry in the coming years., 7 pages, published in proceedings of "Stellar Polarimetry: From Birth to Death" (Madison, WI, June 2011)

The Robert Stobie Spectrograph is currently the prime spectroscopic instrument on the 11m Southern African Large Telescope (SALT), which is now in commissioning. The current visible beam of RSS was designed with spectropolarimetric versions of all its modes, imaging, grating spectroscopy (with Multi Object Spectroscopy capability) from 3200 to 9000 A, and Fabry-Perot Spectroscopy from 4300 to 9000 A, with spectral resolution up to R = 10000. The polarimetric field of view is 4×8 arcmin. The instrument was designed with an upgrade path leading to a simultaneous Near InfraRed beam (out to 1.7µm), now in development, which will duplicate the spectropolarimetric modes in the NIR. We describe results from early polarimetric commissioning of the visible beam.

While time resolved astronomical observations are not new, the extension of such studies to sub-second time resolution is and has resulted in the opening of a new observational frontier, High Time Resolution Astronomy (HTRA). HTRA studies are well suited to objects like compact binary stars (CVs and X-ray binaries) and pulsars, while asteroseismology of pulsating stars, occultations, transits and the study of transients, will all benefit from such HTRA studies. HTRA has been a SALT science driver from the outset and the first-light instruments, namely the UV-VIS imager, SALTICAM, and the multi-purpose Robert Stobie Spectrograph (RSS), both have high time resolution modes. These are described, together with some observational examples. We also discuss the commissioning observations with the photon counting Berkeley Visible Image Tube camera (BVIT) on SALT. Finally we describe the software tools, developed in Python, to reduce SALT time resolved observations.

Of the two first-light instruments commissioned for the Southern African Large Telescope (SALT) the Robert Stobie Spectrograph (RSS) represents the most intricate instrument to control on SALT. As such the RSS control software (RCON) called for a design that would handle the necessary elaborate configuration commands required to coordinate the various hardware mechanisms of RSS into the desired states. In this paper we describe in detail the software architecture, developed in LabVIEW, used to control the RSS hardware mechanisms. A command ID based array system was developed to allow the multi-faceted commands to execute in order to facilitate the shortest configuration times and managing all of the hardware interdependencies.

The Robert Stobie Spectrograph near infrared arm will provide high throughput, low to medium resolution long slit and multi-object spectroscopy with broadband, spectropolarimetric, and Fabry-Perot imaging modes over a 8' diameter field of view. The wavelength range of the instrument is 0.9-1.7 microns, and can be operated simultaneously with the visible arm to extend the short wavelength limit to 0.32 microns. Once fielded, RSS-NIR will be the only facility instrument on an 8-10 meter class telescope with multi-object spectroscopy capability covering this spectral range simultaneously. RSS-NIR is scheduled to be commissioned on the 11-meter Southern African Large Telescope in late 2012. This is an upgrade to the existing visible instrument, with which it shares the slit plane and an ambient temperature collimator. Beyond the collimator, the NIR arm is cooled to -40 °C, with a cryogenic dewar containing the detector, long wavelength blocking filters, and final camera optics. This semi-warm configuration has required extensive upfront analysis of the instrumental thermal background levels, which have been incorporated into the instrument performance simulator. We present the performance predictions for spectroscopic modes of RSS-NIR and preliminary performance estimates and NIR issues still being addressed in the design for Fabry-Perot and polarimetric modes.

The Robert Stobie Spectrograph Near Infrared Arm (RSS-NIR) is a new instrument on the 11-meter Southern African Large Telescope (SALT), scheduled to begin commissioning in 2012. This versatile instrument will add capabilities that are unique to large telescopes. The main instrument modes include NIR imaging, medium resolution long slit spectroscopy over an 8 arcminute field of view (FOV), multi-object spectroscopy with custom slit masks over an 8x8 arcminute FOV, Fabry-Perot narrowband imaging over an 8 arcminute diameter FOV, and polarimetry and spectropolarimetry over a 4x8 arcminute FOV. Limiting magnitude predictions are 21.1 and 20.1 for J and H band for S/N = 10 per spectral resolution element in 1 hour for 1 arcsec 2 at an R=7000. All instrument modes can be operated simultaneously with the RSS visible arm, providing spectral coverage from 0.32-1.7 microns. We list the science drivers and describe the way in which they have guided the design for this instrument. We also present a more detailed description of some several planned science programs that will take advantage of the unique capabilities of RSS-VISNIR and the queue-scheduled SALT telescope. Lastly we give a brief description of predicted instrumental performance, along with a comparison to several other NIR instruments at other observatories.

The large (~10 m) aperture of the Southern African Large Telescope (SALT) coupled with the unique capabilities of the Robert Stobie Spectrograph (RSS), promises unparalleled prospects for polarimetric observations on an 8 - 10 m class telescope. RSS is a highly versatile first-generation instrument of the SALT. Results from some of the first commissioning observations with the RSS are presented. A method for reducing SALT RSS spectropolarimetry data is proposed and verified on observations of unpolarised and polarised standard stars. The results provide estimates of telescope and instrumental polarisation as well as a calibration of the instrument's polarimetric position angle offset.

SALT uses the Principal Investigator Proposal Tool (PIPT) for generating, checking, submitting and editing proposals. The PIPT maps XML into Java classes with immediate error and consistency checking, and thus prevents non-feasible observation requests. Various tools allow the user to simulate SALT observations. These include standard source spectra (e.g. black body, power law, Kurucz model atmospheres), and allow users to add their own library spectra. The PIPT is complemented by the Web Manager for administering submitted proposals. It is discussed how the code of these tools can easily be extended for future instruments and used for other projects.

We report on extensive laboratory testing of the optical compatibility of immersion fluids often used in astronomical instrumentation. A strong near-ultraviolet absorption feature is seen after incubating several fluids with polyurethane often used in expansion bladders, and a lesser absorption in the farther UV with Viton O-Ring material. Substitute materials were tested, many of which show no such absorption. This program was started in response to a strong UV feature which developed over time in the Robert Stobie Spectrograph of the Southern African Large Telescope. A repair strategy was successfully implemented.

The University of Wisconsin's Space Astronomy Laboratory has designed and built a Star Tracker suitable for use on sounding rockets and class D satellites. This device brings together autonomous attitude determination ("Lost in Space" mode), multi-star tracking, and a novel form of Progressive Image Transmission (US patent #5,991,816), which allows the device to be used as an ultra-low bandwidth imager. The Star Tracker 5000 (ST5000) reached operational status in a suborbital sounding rocket flight in August 2007. The ST5000 determined the rocket's inertial (FK5) attitude with arcsecond precision using its autonomous attitude determination capability, and then provided continuous sub-arc-second tracking for the full 360-second on-target portion of the flight. The ST5000 RMS tracking error was 0.54 arc-seconds in yaw and pitch, and 17 arc-seconds in roll. The vehicle RMS jitter was 0.5 arc-seconds in yaw and pitch, and 10 arc-seconds in roll. The ST5000 was funded by NASA grants NAG5-7026 and NAG5-8588.

The Southern African Large Telescope is nearing the end of its commissioning phase and scientific performance verification programmes began in 2006 with two of its First Generation UV-visible instruments, the imaging camera, SALTICAM, and the multi-mode Robert Stobie Spectrograph (RSS). Both instruments are seeing limited and designed to operate in the UV-visible region (320 - 900 nm). This paper reviews the innovative aspects of the designs of these instruments and discusses the commissioning experience to date, illustrated by some initial scientific commissioning results. These include long-slit and multi-object spectroscopy, spectropolarimetry, Fabry-Perot imaging spectroscopy and high-speed photometry. Early spectroscopic commissioning results uncovered a serious underperformance in the throughput of RSS, particularly at wavelengths < 400nm. We discuss the lengthy diagnosis and eventual removal of this problem, which was traced to a material incompatibility issue involving index-matching optical coupling fluid. Finally, we briefly discuss the present status of the third and final First Generation instrument, a vacuum enclosed fibre-fed high resolution, dual beam, white pupil echelle spectrograph, SALT HRS, currently under construction.

(abridged) We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These data are combined with archival HST imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components. One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disk and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7x10^10 M_solar for both. The third component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for AGN activity is found from optical or mid-infrared data. The star formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the Bird shows kinematic, dynamical, and emission line properties typical for cool ultra luminous IR galaxies. However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation does not come from the two major K-band nuclei, but from the third irregular component. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components., 24 pages, 16 figures. Accepted MNRAS version, minor corrections only, references added. Higher resolution version (1.3MB) is available from http://www.saao.ac.za/~petri/bird/ulirg_bird_highres_vaisanen_v2.pdf

We report long-slit spectroscopic observations of the dust-lane polar-ring galaxy AM1934-563 obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. The observations target the spectral region of the Ha, [NII] and [SII] emission-lines, but show also deep NaI stellar absorption lines that we interpret as produced by stars in the galaxy. We derive rotation curves along the major axis of the galaxy that extend out to about 8 kpc from the center for both the gaseous and the stellar components, using the emission and absorption lines. We derive similar rotation curves along the major axis of the polar ring and point out differences between these and the ones of the main galaxy. We identify a small diffuse object visible only in Ha emission and with a low velocity dispersion as a dwarf HII galaxy and argue that it is probably metal-poor. Its velocity indicates that it is a fourth member of the galaxy group in which AM1934-563 belongs. We discuss the observations in the context of the proposal that the object is the result of a major merger and point out some observational discrepancies from this explanation. We argue that an alternative scenario that could better fit the observations may be the slow accretion of cold intergalactic gas, focused by a dense filament of galaxies in which this object is embedded (abridged)., Comment: 19 pages, 13 figures, submitted to MNRAS. Some figures were bitmapped to reduce the size. Full resolution version is available from http://www.saao.ac.za/~akniazev/pub/AM1934_563.pdf

The Prime Focus Imaging Spectrograph (PFIS) is a first light instrument for the Southern African Large Telescope (SALT). PFIS is a versatile instrument designed to operate in a number of scientific modes by utilizing volume phase holographic gratings, Fabry-Perot etalons, and polarimetric optics, which are manipulated in and out of the beam using various placement mechanisms. The instrument is mounted at the prime focus 15m above the primary mirror and tilted at 37°. This remote placement and the need for 240° of rotation about the optical axis raises important design issues with mass, flexure and access. The instrument structure provides the interface to the telescope Prime Focus Instrument Platform (PFIP) as well as support points for all the optics, mechanisms and electrical equipment. The structure is a welded open truss of hollow, square-section Invar beams. The open truss provides the highest stiffness to weight ratio and minimizes the effect of wind loading, while the use of Invar negates the effects of thermal expansion. It has been designed using finite element analysis in conjunction with an optical tolerance analysis of the optics nodes to minimize effective image motion under the varying gravity load. The fundamentals of the design of the structure to minimize the flexure and its effect on image motion, the motivation for using the open Invar truss structure, and the design of the remotely operated mechanisms are discussed. In 2005 PFIS was installed and commissioned on SALT in South Africa. Included in this text are some of the results and experiences of taking PFIS into operation.

"First light" of the Southern African Large Telescope was declared on 1 Sep 2005 and the first scientific programs have now begun. This paper discusses the completion and commissioning of the first-light instruments: the UV-visible imaging camera, SALTICAM, and the prime focus imaging spectrograph, the Robert Stobie Spectrograph (RSS). The innovative aspects and tight constraints on the design of these prime focus instruments are described, as well as the first scientific results. These instruments, which are all seeing limited, operate in the UV-visible region (320 - 900 nm), and will provide capabilities for broad and narrow band imaging, long-slit and multi-object spectroscopy (R ~ 6000 for seeing limit), spectropolarimetry and Fabry-Perot imaging spectroscopy (R ~ 320-9,000). Time resolved studies are an important aspect of the overall SALT science drivers and special efforts were made to ensure an ability to run at ~10 Hz, with minimal dead time, by employing frame transfer CCDs. Finally, we present the design and status of the fiber-fed high resolution echelle spectrograph, SALTHRS, the last of the "first generation" SALT instruments.

The near infrared (NIR) upgrade to the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT), RSS/NIR, extends the spectral coverage of all modes of the visible arm. The RSS/NIR is a low to medium resolution spectrograph with broadband imaging, spectropolarimetric, and Fabry-Perot imaging capabilities. The visible and NIR arms can be used simultaneously to extend spectral coverage from approximately 3200 A to 1.6 um. Both arms utilize high efficiency volume phase holographic gratings via articulating gratings and cameras. The NIR camera is designed around a 2048x2048 HAWAII-2RG detector housed in a cryogenic dewar. The Epps optical design of the camera consists of 6 spherical elements, providing sub-pixel rms image sizes of 7.5 +/- 1.0 um over all wavelengths and field angles. The exact long wavelength cutoff is yet to be determined in a detailed thermal analysis and will depend on the semi-warm instrument cooling scheme. Initial estimates place instrument limiting magnitudes at J = 23.4 and H(1.4-1.6 um) = 21.6 for S/N = 3 in a 1 hour exposure well below the sky noise., Comment: 12 pages, 10 figures, presented at SPIE, Astronomical Telescopes and Instrumentation, 24 - 31 May 2006, Orlando, Florida USA

The Southern African Large Telescope (SALT), which had its ground-breaking in September 2000, is rapidly nearing completion, with commissioning planned for most of 2004 and first science observations due to begin in early 2005. This paper describes the design and status of the SALT instrumentation, including the facility instruments (e.g. atmospheric dispersion compensator, guidance system, etc) and the First Generation science instruments: SALTICAM, a high-speed optical imager, PFIS, a versatile prime focus imaging spectrograph and SALT HRS, a fiber-fed high resolution echelle spectrograph. These first instruments are confined to the UV-visible region, and in the case of the first two, optimized for UV-blue performance, with a capability down to ~320 nm. The First Generation instruments, which are all seeing limited, will provide the following capabilities: broad and narrow band imaging, long-slit and multi-object spectroscopy (up to R ~ 6000), spectropolarimetry, Fabry-Perot imaging spectroscopy and precision high resolution spectroscopy (up to R ~ 80,000). Time resolved studies are an important aspect of the overall SALT science drivers and special efforts are being made to ensure an ability to run at >10 Hz, with minimal dead time, by employing frame transfer CCDs on two of the instruments (SALTICAM and PFIS). SALTICAM was installed on SALT in October 2003, while its full imaging mode will be commissioned in 2004. PFIS is currently on schedule for integration on SALT in December 2004, while SALT HRS is due to complete its Preliminary Design Review in July 2004.

The Hanle effect has been proposed as a new diagnostic of circumstellar magnetic fields for early-type stars, for which it is sensitive to field strengths in the 1-300 G range. In this paper we compute the polarized P-Cygni line profiles that result from the Hanle effect. For modeling the polarization, we employ a variant of the ``last scattering approximation''. For cases in which the Sobolev optical depths are greater than unity, the emergent line intensity is assumed to be unpolarized; while for smaller optical depths, the Stokes source functions for the Hanle effect with optically thin line scattering are used. For a typical P Cygni line, the polarized emission forms in the outer wind, because the Sobolev optical depth is large at the inner wind. For low surface field strengths, weak P Cygni lines are needed to measure the circumstellar field. For high values of the surface fields, both the Zeeman and Hanle diagnostics can be used, with the Zeeman effect probing the photospheric magnetic fields, and the Hanle effect measuring the magnetic field in the wind flow. Polarized line profiles are calculated for a self-consistent structure of the flow and the magnetic geometry based on the WCFields model, which is applicable to slowly rotating stellar winds with magnetic fields drawn out by the gas flow. For surface fields of a few hundred Gauss, we find that the Hanle effect can produce line polarizations in the range of a few tenths of a percent up to about 2 percent., accepted to the Astrophysical Journal

We present the results of a Monte Carlo radiative transfer code that calculates the polarization produced by multiple Thomson scattering and variable absorptive opacity in a circumstellar disk around one component of a close detached binary system. We consider in detail the polarization variations over the binary cycle that result from the disk's illumination by the external star and by its own volume emission. We identify key features of these polarization phase curves and investigate their behavior as functions of optical depth, albedo, and inclination for geometrically thin and thick disks. The polarization due to disk self-illumination is sensitive to the internal optical characteristics of the disk, while the polarization arising from external illumination is mainly sensitive to the disk's geometrical thickness. With appropriate flux weighting, these results, combined with those for an internally illuminated disk, allow simulation of the polarization signature from an arbitrary binary-disk system., 34 pages, 17 figures. Submitted to ApJ, revised in response to referee comments. Color figures available from http://www.ruf.rice.edu/~jhoffman/monte/colorfigs.html

The Prime Focus Imaging Spectrograph (PFIS) will be the workhorse first-light instrument on the Southern African Large Telescope (SALT). Scheduled for commissioning in late 2004, PFIS is a versatile high-throughput imaging spectrograph with a complement of 5 volume-phase holographic gratings for spectroscopic programs from 3200a to 9000a at resolutions of R=1500 to R=6000. A magazine of 6 longslits and 30 custom laser-milled slitmasks enables single- or multi-object spectroscopy over an 8 arcminute diameter field. With the gratings stowed, a dual-etalon Fabry-Perot subsystem enables imaging spectroscopy at R=500, R=3000, and R=12,500. The polarization subsystem, consisting of a polarizing beam-splitter used in conjunction with half- and quarter-wave plates, allow linear or circular polarimetric measurements in ANY of the spectroscopic modes. Three mosaiced rapid-readout frame-transfer CCDs provide the capability for time-resolved sampling at rates in excess of 10 Hz. Combinations of these subsystems permit novel observing modes for specialized scientific programs. Examples include high-time resolution multi-object spectral polarizmetry of accreting compact objects, and Fabry-Perot polarimetry or imaging spectral polarimetry of nebulae and stellar clusters. The demands of queue-scheduled observing on a fixed-altitude telescope require that the instrument be capable of rapid reconfiguration between modes.

The University of Wisconsin - Madison, together with Rutgers University and the South African Astronomical Observatory, is designing and building an imaging spectrograph for the Prime Focus Instrument Package of the Southern African Large Telescope (SALT). The Prime Focus Imaging Spectrograph (PFIS) will be a versatile instrument specializing in very high throughput, low and medium resolution (R=500-12,500) imaging spectroscopy, using volume phase holographic (VPH) gratings and a double etalon Fabry-Perot interferometer, and spectropolarimetry from 320 to 900 nm. The optical design includes all transmissive optics for high efficiency and compactness. To maintain throughput in the ultraviolet, only fused silica, CaF2 and NaCl are used. As NaCl is very hygroscopic, the design uses NaCl as the inner element in sealed triplets only. For the highest possible first-order spectral resolution, the collimated beam size is 150 mm - the maximum for practical Fabry-Perot etalons. The F/2.2 camera can be articulated to tune the efficiency of the VPH gratings; a complement of six gratings (5 VPH and 1 standard transmission grating) has been designed to fill the resolution-wavelength space available to the instrument. Linear, circular, and all-stokes spectropolarimetry will be performed through the use of Pancharatnam superachromatic waveplates and a Wollaston beamsplitter.